Main Session
Sep
29
PQA 06 - Genitourinary Cancer, Gynecological Cancer, and Health Care Access and Engagement
Presenter(s)
Ryan Zitter, MD, MSc - University of Chicago, Chicago, IL
R. Zitter1, D. K. Dietrich2, S. Ansari3, S. Y. Kim-Wang4, Z. Tian5, T. Wu4, C. H. Son4, and Y. Hasan6; 1University of Chicago, Chicago, IL, 2University of Chicago Pritzker School of Medicine, Chicago, IL, 3Northwestern University, Chicago, IL, 4Department of Radiation and Cellular Oncology, University of Chicago, Chicago, IL, 5Department of Radiation & Cellular Oncology, The University of Chicago, Chicago, IL, 6Department of Radiation and Cellular Oncology, University of Chicago Medical Center, Chicago, IL
Purpose/Objective(s):
Persistent cervical FDG uptake after definitive chemoradiation (CRT) and brachytherapy creates uncertainty between residual disease and treatment changes. While new distant FDG-avid lesions predict recurrence at those sites, their association with persistent cervical disease is unclear. We aimed to identify PET-based predictors of biopsy-proven residual cervical disease and develop quantitative triage rules to guide biopsy decisions in the setting of equivocal exam findings.Materials/Methods:
We performed a retrospective multi-institutional study of patients treated with CRT and MRI-guided brachytherapy who underwent PET imaging 3 months post-CRT (2011–2022). Subsequent PETs were also evaluated. Clinical variables assessed included stage, histology, comorbidities, and treatment factors. For biopsy-focused analysis, we included post-brachytherapy PET scans followed by cervical biopsy within 8 weeks. PET variables included cervical SUVmax, tumor-to-liver ratio, and new FDG-avid lesions. Associations were assessed with Fisher’s exact and Wilcoxon rank-sum tests. Logistic regression estimated odds ratios (OR) with 95% confidence intervals (CI). Diagnostic performance metrics (sensitivity, specificity, PPV, NPV) were calculated for biopsy triage value.Results:
Seventy-one patients were included in initial analysis. Demographics included median age 39 years (23-88), predominantly squamous cell carcinoma histology (90%), and a majority with FIGO 2008 stage II–III disease (26 Stage II, 17 Stage III). Twenty-three patients had complete radiographic response on 3-month PET, while 21 had cervical avidity with SUV greater than background and <5. In totoal, 338 PET scans were reviewed. Thirty-two patients underwent 38 biopsies (prompted by equivocal exam findings) and 38 PET scans within 8 weeks of biopsy. Of these, 6 biopsies (from 5 patients) demonstrated persistent cervical carcinoma. The presence of new PET avidity elsewhere was associated with a 5-fold increased odds of cervical cancer persistence (OR 5.2, 95% CI 0.81–33.6; Fisher exact p=0.094; logistic regression p=0.083). Cervical SUVmax alone was not independently predictive, and normalization to liver uptake did not improve discrimination. Absence of new avidity elsewhere yielded a negative predictive value (NPV) of 90% for cancer persistence at the cervix (sens 25%, spec 79%, PPV 12.5%), which increased to 95% when combined with cervical SUVmax <5 (sens 75%, spec 47%, PPV 14%). No significant associations were observed for age, baseline tumor size, smoking status, race, stage, or histology. Pre-treatment PET SUV and change in PET value did not correlate to likelihood of positive biopsy.Conclusion:
In this cohort, absence of new PET avidity combined with cervical SUVmax <5 demonstrated high NPV (95%) for persistent cervical disease. With further validation, clinical application of this rule may safely defer biopsy in select patients with equivocal cervical exam findings post CRT.